The present invention relates generally to vacuum-operated waste liquid control systems utilizing inlet vacuum valves and operative control means, and more specifically to an integral package system thereof containing a sump, vacuum valve, and sensor-controller, which is compact and portable, and may be easily installed.
An operational vacuum system for transporting waste liquids, such as sewage, is disclosed in U.S. Pat. No. 4,179,371 issued to Foreman et al. Each waste liquid inlet point includes a vacuum valve and controller assembly, which allows intermittent passage of waste liquid accumulated in a holding tank or sump into an associated transportation conduit network connected at the other end to a collection tank, and thereafter ultimately to a treatment plant. As taught by the '371 patent, this conduit is typically laid with a saw-toothed profile with a combination of riser, low point, and downslope portions (collectively called a "lift") repeated throughout the length of the conduit main to accommodate the topography (e.g., other conduits and rock layers), as well as incoming flows (from an individual vacuum valve or branch main). The conduits of the '371 patent are buried beneath ground level, and are used to transport sewage.
The slope of the downsloped portions of the profile is such that the drop between lifts is generally equivalent to at least 40% of the conduit diameter (80% if the diameter is smaller than 6") or 0.2% of the distance between lifts, whichever is greater. Generally, the transport conduit network is continuously maintained under vacuum or subatmospheric pressure. Upon opening of the vacuum valve to commence a transport cycle, waste liquid and air, usually at atmospheric pressure, are swept through the conduit by means of applied differential pressure until the valve is closed at which point any residual waste liquid not transported through the conduit during the transport cycle comes to rest in a low point therein, thereby permitting vacuum or subatmospheric pressure to generally be communicated and maintained throughout the entire conduit section.
Vacuum valves function within this system by sealing and unsealing the passage between two parts of an evacuated system to define a transport cycle. The general structure and method of operation of this type of vacuum valve is described in U.S. Pat. No. 4,171,853 issued to Cleaver et al., as well as U.S. Pat. Nos. 5,078,174 and 5,082,238 assigned in common to the owner of the present invention.
Operation of the vacuum valve may, in turn, be controlled by a sensor and a controller, either separated or combined, which contain parts operated by means of differential pressure and the hydrostatic pressure condition existing in the sump to determine whether an atmospheric or subatmospheric pressure condition should be communicated to the valve to close or open it, respectively. The general structure and method of operation of such a sensor controller is described in U.S. Pat. Nos. 4,373,838 and 3,777,778.
Numerous applications for vacuum transport systems other than sewage exist. For instance, freezer units used in supermarkets, convenience stores, etc. must be periodically defrosted, thereby creating a source of waste water. Gray water collection from baths and sinks in a residence likewise give rise to waste liquids. Indeed, even a drinking fountain in a school or commercial establishment drains unconsumed water which may be contaminated with other liquids which were poured into the fountain.
The waste water effluents from all of these systems must be sent to a treatment facility. This objective could be achieved by using a sewage vacuum valve and sensor-controller known in the trade in conjunction with a transport conduit buried in the floor of the commercial or residential establishment. However, such systems are generally bulky, expensive, and complicated to install, and better suited for volumes of waste liquids exceeding those arising from freezer units, drinking fountains, sinks, and baths. Moreover, they involve a large number of components (e.g., valve, sensor-controller, sump, pipe, fittings, and mounting brackets), which must be purchased separately and assembled in a space-consuming system.